All U.S. and foreign patents cited within this specification are hereby incorporated by reference.
The nature of the gravure process imposes certain fundamental requirements on the chemical, physical and strength characteristics of the required inks. Toners are necessary to provide jet black appearances of inks containing standard black pigments, such as, carbon black, as one prominent example. Such a toner must be compatible in gravure ink vehicles, must not alter the mobility, the low viscosity, and the fundamental fast drying properties of the ink necessary for the Gravure process. Currently, alkali blue, from BASF, known as Pigment 61 (Colour Index # 42765:1) is utilized as the most prevalent black pigment toner in such gravure ink operations. Unfortunately, although such a toner meets the required solubility properties, the toning effects provided thereby simultaneously are less than satisfactory due to an excessive reddening and/or bronzing of the black printed image. An improved toner reducing such unwanted effects is thus highly desired within the black Gravure ink industry and market. To date, there are no teachings or fair suggestions of such needed improvements provided by and within the pigment for gravure ink prior art. It is believed that certain chromophores with an appropriate pendant group system may not only provide such desired solvent (toluene, ketones, etc) solubility, but may also provide effective toning with low-reddening and low-bronzing levels within such black gravure inks.
U.S. Pat. No. 4,383,865, to Iyengar, discloses a process for preparing a soft textured, high strength Alkali Blue pigment composition which comprises insolubilized amines. This composition is made by mixing a solution of alkali blue crude first with an alkaline solution of an alkyl aryl sulfonic acid, then with an acidic solution having from 3 to 36 carbon atoms, following which the pigment composition is recovered. In the '865 patent the preferred group of alkyl aryl sulfonic acids has from 1 to 14 carbon atoms. The most preferred alkyl aryl sulfonic acid appears to be dodecylbenzene sulfonic acid.
The closest related art of which applicants are aware includes the following U.S. Pat. Nos. 5,026,627; 4,456,485; 4,383,865; 4,032,357. U.S. Pat. No. 5,026,627 discloses a particular combination of surfactants, when incorporated with an Alkali Blue Pigment 61, produce a pigment product having the desirable characteristic of exhibiting high strength when used in either water flexo or oil ink end uses. The surfactants utilized are (1) di- and tri-decyl phosphate esters of free acids, together with (2) dehydroabietyl amine. U.S. Pat. No. 4,456,485, to Iyengar, discloses a process for preparing easily dispersible high color strength powdered alkali blue pigments by precipitating the pigment in the presence of various acids and/or amines, and/or esters, and/or alcohols, etc., as well as the product of these processes.
U.S. Pat. No. 4,032,357, assigned to Sherwin-Williams Company, discloses a substantially anhydrous, free-flowing alkali blue pigment composition having an organic anionic dispersant coprecipitated therewith. Furthermore, the pigment and dispersant are admixed with an oil phase in order to reduce the hydrophilic aggregation of the coprecipitated pigment and dispersant. The specific organic dispersants used in the '357 patent are Gafac.RTM. RS-710 and Gafac.RTM. RS-610.
A colorant compound having polymer or pre-polymer substituent groups may be synthesized by the reaction of a colorant and a polyisocyanate as disclosed in Cross et al., U.S. Pat. No. 4,284,729; Krutak et al., U.S. Pat. No. 5,194,463; and Beckmann et al., U.S. Pat. No. 5,616,678.
U.S. Pat. No. 5,026,627 disclose a particular combination of surfactants when incorporated with an alkali blue pigment, produce a pigment toner exhibiting high strength when used in toluene-based inks (as one example of gravure types). While the pigment is widely used throughout the industry, they have serious drawbacks (as discussed above) in that they are difficult to handle, they are not conducive to post addition, provide a reddish tone to carbon black and causes bronzing of the printed image.